Pro-Russian protesters attack a pro-Ukranian protester during a rally in the eastern city of Donetsk April 28, 2014.Reuters

The European Union has slapped sanctions on 15 Russian politicians and military chiefs by imposing travel bans and asset freezes.

The list includes Dmitry Nikolayevich Kozak, who has served as Russia's deputy prime minister since 2008, the deputy chairman of the State Duma, Ludmila Ivanovna Shvetsova, and the chief of staff of Russia's armed forces Valery Vasilevich Gerasimov.

Separatist leaders such as Andrei Purgin, the leader of the Donetsk Republic, a pro-Russian separatist organisation, and Denys Pushylin, another seperatist, also made the list.

Full List

Dmitry Kozak, deputy prime minister responsible for overseeing the integration of the annexed Crimea into Russia.

Oleg Belaventsev, non-permanent member of the Russian Security Council, responsible for implementing constitutional prerogatives of the Russian president in Crimea.

Oleg Savelyev, minister for Crimean Affairs responsible for the integration of Crimea into Russia.

Sergei Menyailo, acting governor of the Ukrainian annexed city of Sevastopol.

Olga Kovatidi, member of the Russian Federation Council from Crimea.

Ludmila Shvetsova, deputy chairman of the State Duma - responsible for initiating legislation to integrate Crimea into Russia.

Sergei Neverov, deputy chairman of the state Duma, responsible for law to integrate Crimea into Russia.

Igor Sergun, director of GRU (Main Intelligence Directorate), deputy Chief of the general staff of Russia's armed forces. He is responsible for GRU officers in Eastern Ukraine.

Valery Gerasimov, chief of the general staff of Russia's armed forces, first deputy minister of defence, army general responsible for "massive deployment" of Russian troops along the border with Ukraine.

German Prokopiv, active leader of the Lugansk Guard who took part in the seizure of the building of the Lugansk regional office of the Security Service, recorded a video address to President Vladimir Putin and Russia from the occupied building. Close links with the "Army of the South-East".

Valeriy Bolotov, one of the leaders of the separatist group Army of the South-East, which occupied the building of the Security Service in the Lugansk region. Retired officer. Before seizing the building, he and others possessed arms apparently supplied by Russia and local criminal groups.

Andriy Purgin, head of the Donetsk Republic

Denys Pushylin, one of the leaders of the Donetsk People's Republic.

Tsyplakov Gennadevich, one of the leaders of "ideologically radical organisation", the People's Militia of Donbass.

Igor Strelkov, identified as staff of the main intelligence directorate of the general staff of Russia's armed forces. He was involved in incidents in Sloviansk. He is an assistant on security issues to Sergey Aksionov, self- proclaimed prime-minister of Crimea. SOURCE: EU/REUTERS

The announcement comes after Britain's Serious Fraud Office (SFO) confirmed that it has opened a criminal investigation into possible money laundering arising from suspicions of corruption in Ukraine.

The SFO said it has obtained a restraint order freezing approximately $23m (£28m, €39m) of assets in the UK in connection with the case.

"For reasons of confidentiality we cannot say more at this time," it added.

In addition and separate to the $23m in assets that have been placed under restraint by the SFO, an EU-wide asset freeze against 22 individuals suspected of misappropriating Ukrainian state assets has been approved and has come into force across the European Union (EU).